Proxy capable of running JavaScript?

This is the first time that I heard this, but is there a proxy capable of running Javascript since the plugin I am using cannot do it.

We need more details here.
Regular proxy doesn't run anything. You need a VPS with root access to run something.

So you need to scrape something via a proxy and have the html returned with any javascript already executed? You could do that with any normal proxy, but use a headless browser to execute the javascript - though this will require that you have programming knowledge, and as you're using a plugin that might not be implementable.

Another way would be to use a scraping API, as most of them will offer javascript support. Some examples:
https://www.scraperapi.com/pricing/https://scrapeops.io/proxy-aggregator/
Some of the services will allow you to access the API via a specially crafted proxy string (example using scrapebox) so if the only option you have is to specify a proxy server, that may work out for you.

use scraping APIs,
almost all top provider offer it, such as, brightdata, soax and so on

To manage operations performed on an object using a proxy, you must first create a proxy object. Here is a simple example:

const target = {
message: 'Merhaba, Dünya!'
};

const handler = {
get: function (obj, prop) {
return obj[prop].toUpperCase();
}
};

const proxy = new Proxy(target, handler);

console.log(proxy.message); // "HELLO!"

There may be some out there, can't say any one in particular comes to mind. Some proxies do provide integrated APIs already, might be worth checking out seller posts on the Marketplace for some details on it.

I haven't heard this before. But I would suggest you can ask in the marketplace. or some proxy providers offers APIs, maybe that can help you